In various applications it is desired to detect two different liquid levels. For example, it may be required that a motor be turned on when the liquid is at one level and turned off when the liquid is at a second, lower level. Another example would be a situation which required one pump to be turned on when the liquid reached a first level and a second pump to be turned on when the liquid reached a second, higher level. An example of an apparatus of this character will be found in my prior U.S. Pat. No. 3,972,647. Conventionally, two separate level detecting devices are employed. Float switches are known for this purpose and the known float switches include one in which a mercury switch is embedded or otherwise incorporated into the float with the float being so mounted that its angle of inclination changes with a change in the level of the liquid. At a predetermined inclination, the mercury in the mercury switch reaches a pair of electrical contacts to close an electrical circuit, or leaves the contacts to open an electrical circuit.
In the present invention, two mercury switches are incorporated into a single float with the switches having different angles of inclination with respect to the axis of the float. Thus, as the angle of inclination of that axis varies with varying liquid levels the switches will be actuated (opened or closed) at points corresponding to different liquid levels. The inclination of one of the switches with respect to the axis of the float is adjustable whereby the difference in liquid levels which will cause actuation of the respective switches may be varied.
In addition to simplification and cost reduction in the cost of manufacture, a structure of this type has a number of advantages. One advantage that may be significant in many installations is the matter of saving of space. Many sumps, for example, are relatively small in horizontal cross-section as compared to the space required for the insertion of the pump mechanisms and their controls. This is particularly true where it is desired to utilize two pumps, one comprising a motor driven from the house electric circuit and the second utilizing a battery powered direct current motor. Some installations will be made where the second pump is also driven from the household light circuit, but employed as a backup in case the water inflow into the sump is greater than can be handled by the primary pump. With such installations it is often difficult to accommodate two float, mercury switches because of the lack of available space remaining after the pumps are placed in the sump. Another significant advantage is ease and time saving in making the installation. The single switch can be installed on the pump mechanism at the time it is manufactured and a few simple adjustments at the time of installation will result in detecting the two different liquid levels as desired.
Another feature of the present invention is the mounting of the float on the end of a plastic tube which has a cutaway portion so that the remainder of the tube at the cutaway area serves as a hinge permitting the float to move in a vertical plane normal to the surface of the liquid while restraining the float against other movement. The switches are positioned so that the movement in that plane results in the mercury moving toward or away from the electrical contacts of the switches. Not only does this construction provide repeatable performance in water level detection, but it is a very economical structure to manufacture.
Further objects and advantages will be apparent from the following description taken in conjunction with the drawings.